The present invention relates to a control rod and more particularly to a control rod suitable for use in a boiling water type nuclear reactor.
A boiling water type nuclear reactor uses a control rod for reaction degree control of the reactor center. The control rod is composed of four blades of a neutron absorption material covered with a U-shaped stainless steel sheath which are arranged crosswise as shown in FIG. 5 of Japanese Patent Application Laid-Open 61-95277. The control rod is connected to the control rod derive unit and inserted into the reactor center by the drive operation of the control rod drive unit or pulled out from the reactor center.
The connection of the control rod to the control rode drive unit is executed as shown below. The pull-up handle provided on the control rod is pulled up, and the lock plug extended into the coupling socket provided at the lower end of the control rod is pulled up, and the coupling spud of the control rod drive unit is inserted into the coupling socket provided at the lower end of the control rod in this state, and the pull-up handle is lowered, and the lock plug is lowered. By doing this, the coupling spud is pressed against the coupling socket and the control rod is connected to the control rod drive unit.
The pull-up handle is provided on the lower part support member of the control rod as shown in FIG. 2 of Japanese Patent Application Laid-Open 61-95277. The structure in the neighborhood of the lower part support member on which the pull-up handle is provided will be explained in detail by referring to FIGS. 12 and 13.
The constitution in the neighborhood of the pull-up handle 12 of the control rod is shown in FIG. 12 and the section XIII--XIII is shown in FIG. 13. The pull-up handle 21 is inserted in the window provided in the lower part support member 7 and connected to the rod 13 inserted in the hole 18 with a nut. The thin parts 21A are formed on the left and right of the pull-up handle 21 and the thin parts 7A are formed in the neighborhood of each of the left and right sides facing on the window of the lower part support member 7. The thin parts 21A are fit between a pair of plates 22 attached to both sides of the thin parts 7A by spot welding 23 respectively. The plates 22 are welded to the thin parts 7A in the state that the ends of the thin parts 21A are opposite to the ends of the thin parts 7A. The pull-up handle 21 mounted inside the window will not be dislocated from the lower part support member 7 by the plates 22.
The aforementioned conventional control rod requires a pair of plates 22 and has many parts. It is necessary to weld the pair of plates 22, and there are many manufacturing processes, and it takes a lot of time to produce a control rod.